Disposable absorbent products like diapers typically include stretchable materials in the waist region and the cuff regions to provide a snug fit and a good seal of the article. Pant-type absorbent articles further include stretchable materials in the side portions for easy application and removal of the article and for sustained fit of the article. Stretchable materials have also been used in the ear portions for adjustable fit of the article. The stretchable materials utilized in these article regions may include elastomeric materials such as films, nonwovens, strands, scrims, and the like. In most cases, these designs deliver uniform and unidirectional stretch, most often in the lateral direction of the article. However, elastomeric materials are relatively expensive so their use in stretchable materials may be desirably optimized. Additionally, if elastomeric materials are used without some type of cover material, the elastomeric materials may tend to exhibit increased drag on skin surface, which may result in discomfort to the wearer of the product.
Stretchable materials may be made in the form of a stretch laminate, which involves one or more elastomeric materials laminated to one or more layers of another material. While the laminate may improve wearer comfort, the laminate may exhibit more limited stretchability and/or considerable resistance to stretch. It would be desirable to address this resistance to stretch in order to make more desirable stretch laminates.
One approach for creating stretch laminates is by a stretch bonding method. Stretch bonded laminates are made by stretching an elastic in a first direction, bonding the stretched elastic to one or more materials such as a nonwoven, and releasing the tension from the elastic so that the materials gather. The elastic may be supplied to the process (e.g., elastic strands purchased from a supplier) or formed in-situ within the process. The resulting laminate typically will be extensible in the same direction in which the elastic was stretched. The gathered nonwoven tends to have a corrugated feel and increased caliper that can improve wearer comfort when such stretch bonded laminates are used in absorbent products. The gathered nonwoven may also exhibit improved opacity; a feature that may be desirable since improved opacity often suggests a high quality product. However, stretch bonding has its problems. Handling stretched elastic strands presents processing difficulties that may reduce the speed of the manufacturing line. Furthermore, achieving secure attachment of elastic strands to the nonwoven may be difficult to achieve and/or to maintain. The cost of elastic strands and the means of attachment (e.g., an adhesive) can become prohibitively high. Furthermore, elastic strands may not be able to impart the requisite elasticity to the stretch laminate, such as multidirectional stretch or variable stretch in a given vector.
Some stretch laminates may be formed from an elastic film instead of discrete elastic strands. While such an approach may impart multi-directional stretch and requisite elasticity, elastic films are usually far more costly than strands. Furthermore, elastic films are generally not breathable, which may result in discomfort to the wearer of the product. While elastic films may be perforated to improve breathability, such perforation comes as an additional step and with additional cost. A further disadvantage of elastic films is that it is difficult and costly to provided variability in the elastic forces of a given film.
An alternate approach that is capable of delivering a multidirectional, non-uniform stretch laminate is disclosed in copending U.S. application Ser. Nos. 10/288,095, 10/288,126, and 10/429,433. This approach involves hot melt application of one or more thermoplastic elastomers onto a substrate (e.g., nonwoven), followed by incremental stretching of the substrate that confers the stretch properties of the elastomer to the substrate in a somewhat magnified form. Suitable application methods disclosed therein include direct gravure, offset gravure, and flexographic printing. Each of these methods allow deposition of any amount of an elastomer in any shape and direction, thus giving a wide variety of design flexibility which ultimately results in improved fit of the overall diaper product. However, the hot melt application method can be improved. Incremental stretching can physically break the fiber to fiber network within a nonwoven. As a result, an incrementally stretched nonwoven may appear shredded and be aesthetically undesirable. The shredded appearance can be avoided by using a nonwoven with a sufficiently high basis weight, but with increased basis weight comes increased cost. Furthermore, it is difficult for the hot melt application method to yield a stretch laminate that exhibits a gathered appearance as found in stretch-bonded laminates. Without a gathered nonwoven, the benefits of corrugated feel and increased caliper are missing. Furthermore, the opacity of stretch laminates resulting from the hot melt method can exhibit reduced opacity as compared to a similarly constructed stretch bonded laminate (i.e., the stretch bonded laminate and hot melt laminate having nonwovens of like construction and basis weight).
In view of the above, it would be desirable to provide a cost effective stretch laminate having elastomeric materials disposed only in specific areas in specific amounts to provide a desired in-use benefit (e.g., sealing, containing, gasketing, body-conforming) for an article. It would also be desirable to provide an efficient and cost-effective process for producing the stretch laminates. Further, it would be desirable to provide a process for producing stretch laminates that exhibit gathering or corrugation such that feel and caliper are improved. It would also be desirable to provide a process for producing stretch laminates that exhibit a high degree of opacity.